The Nervous System Essay Paper

The Nervous System Essay Paper

Instructions: When you have mastered the objective, place a check mark in the box.

At the completion of this exercise, you will be able to:

1. Analyze the structure of monosynaptic and polysynaptic reflex arcs,

by using diagrams to compare and contrast their structural features. ☐ 2. Comprehend somatic and autonomic reflexes, by demonstrating their effects, and

explaining how each structural component of a reflex arc contributes to its function. ☐ The Nervous System Essay Paper

3. Analyze the structural and functional features of somatic and autonomic reflex arcs. ☐

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INTRODUCTION

Figure 1. Reflex Arc Classifications

A reflex is a fast, predictable, and involuntary motor response to a stimulus. Reflex responses are

typically protective in nature and function to prevent damage to various bodily tissues. Some reflexes

are used to keep physiological variables, such as blood pressure and respiratory rate, within a narrow

homeostatic range. Reflex responses are made possible by a neuronal structure consisting of a series of

neurons, which together are termed a reflex arc. The Nervous System Essay Paper

A simple reflex arc begins with an afferent sensory neuron that detects a specific stimulus. The

afferent sensory neuron carries sensory information, propagated by graded and action potentials, to an

integrating center, usually located within the central nervous system (CNS). In the integrating center,

action potentials are directed to an effector organ through an efferent motor neuron. The effector

organ produces a response that is either protective or involved in maintaining homeostasis. Often, the

effector is skeletal muscle tissue, which produces a variety of reactive movements, such as a jerk

reaction. The Nervous System – Somatic & Visceral Reflexes.

There is diversity of reflex responses in the body, and may be classified based on various

characteristics. Innate reflexes are present genetically or during development, such as the Babinski

reflex. Normal infants will respond with an upward extension of the toes when the lateral aspect of the

Development

Innate reflexes

Aquired reflexes

Response

Somatic reflexes

Autonomic reflexes

Circuit complexity

Monosynaptic reflexes

Polysynaptic reflexes

Processing site

Spinal reflexes

Cranial reflexes

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sole of the foot is firmly stroked. Absence of this reflex may indicate abnormal development. Acquired

reflexes are learned through experience and practice and may require more complex response patterns. The Nervous System – Somatic & Visceral Reflexes.

For example playing the piano or typing becomes an acquired reflex, but unlike innate reflexes, signals

very complex efferent signals. Somatic reflexes produce a response by the activation of skeletal

muscles through efferent signals propagated by somatic motor neurons. In contrast, autonomic reflexes

result in autonomic motor neurons producing responses in smooth muscle, cardiac muscle, or glands.

The simplest reflex arc structure may contain only two neurons, an afferent sensory neuron and

an efferent motor neuron. Such reflex arcs, lacking interneurons, are termed monosynaptic.

Monosynaptic neurons are called such, because there is only a single synapse in the entire reflex arc.

However, polysynaptic reflex arcs contain one or more interneurons between the afferent sensory

neuron and efferent motor neuron, and so will contain at least two synapses.

In this lab, you will explore the effects of various sensory modalities on production of somatic

and visceral reflexes The Nervous System Essay Paper